# About the meaning of the colorimeter value

Regarding chromatic aberration is a problem that cannot be ignored in all walks of life. In order to make the color design more precise and perfect, we formulate and adjust the appropriate scale and proportion for color conversion and correction, and reduce the copy error caused by the uneven space, so that the geometry is equal in different directions and different positions. The distance has the same chromatic aberration visually. Need to constantly look for the most uniform color space. This carrier is the colorimeter.

The value of the color difference is expressed by the internationally accepted color space. Common ones are RGB, XYZ, LAB, LCH, YXY, etc., but the most concerned by customers is LAB, which can represent any kind of color. The others are basically for reference only. They pay very little attention.

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"L" represents the brightness of the object: 0-100 means from black to white

"A" represents the red-green color of the object: a positive value represents red, and a negative value represents green

"B" represents the yellow-blue color of the object: a positive value represents yellow, and a negative value represents blue

For example, if the measured LAB value of an object (as shown in the figure below) is L: 22.75, A: 22.58, B: 13.83, then the meaning of this set of values is that the (L) brightness value is 22.75, (A ) Red is 22.58, (B) Yellow is 13.83.
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Another example: L: 81.13, A: 1.17, B: 44.65. Then, the meaning of this set of values is that (L) the brightness value is 81.13, (A) red is 1.17, and (B) yellow is 44.65.
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In the measurement process, the first measurement is sampling, that is, testing the standard sample, and the subsequent measurement is the measurement of color difference, that is, measuring the color difference between the tested product and the sample. The difference is the value of the tested product minus the sample value, and the result is Brightness difference △L, red-green difference △A and yellow-blue difference △B.

Its calculation formula is:

△L=L sample-L standard (lightness difference)

△a=a sample-a standard (red/green difference)

△b=b sample-b standard (yellow/blue difference)

△L+ means white, △L- means black

△a+ means reddish, △a- means greenish

△b+ means yellowish, △b- means blueish

where △L*, △a*, △b* are the difference between the lightness L* and the color index a*, b* between the reference sample and the tested sample.

The color difference value is expressed by △E, which is a comprehensive color difference meter. The specific calculation method is related to the brightness difference △L, the red-green difference △A, and the yellow-blue difference △B.

Its formula is:

△E=[(△L)+(△a)+(△b)]1/2

Customers mainly use color matching according to comprehensive color difference △E, brightness difference △L, red-green difference △A and yellow-blue difference △B.

△L is a positive value, indicating that the tested product is brighter than the sample, and a negative value indicates that the tested product is darker than the sample;

△A is a positive value, which means the tested product is redder than the sample, and a negative value means the tested product is greener than the sample;

△B is a positive value, indicating that the tested product is more yellow than the sample, and a negative value indicates that the tested product is more blue than the sample;

For example: △E: 6.1, △A: -21.5 △B: 27.6

means that the tested product is 6.1 brighter than the sample, 21.5 greenish, and 27.6 yellowish.

The meaning of several other color spaces can also be easily understood.

In the LCH color space, L is brightness, C is saturation, and H is hue. Brightness, saturation and hue are the three basic attributes of color.

In the RGB color space, R is red, G is green, and B is blue. This color space is used more in the printing industry.

In the XYZ color space, the XYZ value is used to analyze the color through the reflection characteristics of the surface of the object and its value.
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